The goals of this study are 2-fold: 1) to characterize prenatal phthalate exposures among urban minority mothers and newborns using environmental and biologic monitoring; and 2) to examine effects of exposure on placental function, gestational age and fetal growth. The research is timely. Phthalates are widely used in consumer products and exposures are ubiquitous. 75% of the U.S. population is exposed; women receive higher exposures than men. This has implication for pregnancy as a number of phthalates are endocrine disrupters and have been shown experimentally to modulate steroidogenesis in the placenta, downregulate estradiol and testosterone levels and adversely affect fetal growth. Our pilot data in human populations also indicate that prenatal exposures are reducing gestational age. The proposed study is the first to characterize phthalate exposures specific to urban minorities and to assess endocrine disruption in the placenta and its implication for gestational age and fetal growth. The research is cost-effective in that it will be nested within a well-designed prospective cohort study being conducted by the Columbia Center for Children's Environmental Health. Costs of enrollment, collection and storage of environmental and biologic samples, questionnaires and medical record data are covered under the existing funding. Prenatal phthalate exposures will be characterized in 300 mother/newborn pairs using questionnaires, personal and indoor air monitoring and the measurement of phthalates in biologic samples collected from the mothers and newborns. Repeat measures in a subset will enable evaluation of temporal variability in exposure levels. The study will assess associations between prenatal phthalates, expression of genes involved in steroidogenesis, oxidative stress, and xenobiotic metabolism in the placenta, gestational age and infant birth weight, length and head circumference. The research brings together a collaborative team from Columbia and Harvard Universities, the Centers for Disease Control and Southwest Research Institute with expertise in molecular epidemiology, exposure assessment and health effects of phthalates.